Downhole tools such as packers and bridge plugs come in a variety of forms. A typical mechanically set packer has slips that are driven along tapered cones to hold the set of a seal element that had previously been compressed. The force to do this can come from hydraulic pressure acting on a piston to create relative movement to compress the sealing element driving it out against the surrounding tubular and then radially displacing the slips to complete the set. One example is U.S. Pat. No. 6,467,540. The setting force can come from setting down weight or by use of available wellbore hydrostatic pressure. Other types of packers simply comprise of inflatable bladders that are set through a valve mechanism by applied pressure or wellbore hydrostatic pressure.
More recently designs of packers and bridge plug has involved setting them by expansion of their core. In the past an outer ring was provided that was thin enough to not present too much resistance to expansion while structurally strong enough to support a sealing element such as an elastomer. These designs featured rings extending radially into the elastomer during run in. On expansion, the tips of the rings would extend beyond the elastomer and contact the surrounding tubular. Such contact was intended to blunt the tips of the radially extending rings so as to create a metal to metal contact interspersed with the contact the elastomer would make with the surrounding tubular. This design offered operators the same type of seal the mechanically set packers provided, where a sealing element is compressed into contact with a surrounding tubular but also offered the requirement of some operators to have metal to metal contact as an additional seal.
This design worked well in the context of a tool expanded from within but it proved to have limits in its ability to resist differential pressure beyond a predetermined level that proved too low for some applications. What is needed is a way to retain the sealing benefits of the design while enhancing its grip capabilities under higher differential pressures. Those skilled in the art will better appreciate the scope of the present invention from a review of the description of the preferred embodiment, the drawing and the claims that appear below and indicate the full scope of the invention.